<html>
    <head>
        <title>Test</title>
        <style>

plaintext { size:*; }

        </style>
        <script>

var el = document.querySelector("plaintext");

var counter = 0;

document.on("click","button#append",function() {

  el.plaintext.appendLine("line " +  ++counter);

});


        </script>
    </head>
    <body>

<button#append>append</button>

<plaintext></plaintext>


    </body>
</html>